Along with the recent spread of digital image equipment, such as digital cameras, it is becoming possible to acquire images with excellent image quality by digital image processing. In the case of portable image sensing equipment, such as a digital camera, the so called “hand-shake correction processing” is available, which exhibits an effectiveness to improve the image quality of portable image equipment.
Examples of the hand-shake correction method are optical shake correction and shake correction by image processing. The former is for correcting shaking by mechanically detecting blurring and moving the optical system, and this is used for equipment where the space for mounting this mechanism is available. The latter, as implementing by image processing, is suitable for compact equipment where the mounting space is limited. In the case of a compact digital camera or portable telephone with a camera, images captured consecutively in a short exposure time are combined (added). An image captured in a short exposure time is less affected by hand shaking, but the light quantity is insufficient, so a plurality of images continuously shot are combined, and images of which noise is low and shake is suppressed can be generated.
As the combining method (image processing method), a first prior art which was proposed is a method of detecting the position shift of two entire images, A and B, correcting the position shift of the two entire images A and B according to a common position shift parameter of the two entire images, and combining the two images A and B (e.g. see Patent Document 1), as shown in FIG. 32.
A second prior art which was proposed is a method for acquiring a long time exposure image B and a short time exposure image A consecutively, detecting whether the object moved, and selecting the long time exposure image B if there is movement, and combining the two images A and B if there is no movement (e.g. see Patent Document 2), as shown in FIG. 33. A third prior art which was proposed is acquiring a long time exposure image (for background) B and a stroboscopic image (for object) A consecutively, detecting the blurring of the boundary area between background and object images, and processing the boundary area when the two images are combined so that the boundary area does not become unnatural (e.g. see Patent Document 3). In this processing method, an area where the blurring of the object image, which occurred when the object moved, is replaced with the pixels of image B captured by the stroboscope.    Patent Document 1: Japanese Patent Application Laid-Open No. H11-185018    Patent Document 2: Japanese Patent Application Laid-Open No. 2000-050151    Patent Document 3: Japanese Patent Application Laid-Open No. 2004-194106